1. Technical Field
The present invention relates to a light source device, a lighting and driving method of the light source device and a projector.
2. Related Art
Light source devices including: a high pressure discharge lamp in which a discharge is generated between a pair of electrodes; a lighting device that supplies drive current (alternating current) to the high pressure discharge lamp in order to light and drive the high pressure discharge lamp; and a control device that controllably drives the lighting device, have been known.
In the light source devices, when the high pressure discharge lamp is lighted and driven with drive current of a relatively low frequency, a projection (a discharge trigger) is formed on an tip end of the electrodes of the high pressure discharge lamp (hereinafter referred to as a first projection). In such a lighting and driving, wear on the tip end of the electrodes of the high pressure discharge lamp can be avoided, thereby increasing the longevity of the high pressure discharge lamp.
However, in such a lighting and driving of the high pressure discharge lamp, since the temperature of the electrodes of the high pressure discharge lamp is relatively low, even when the first projection is formed, arc position is moved, so that an arc cannot be stabilized and a flicker may occur. Similarly, when the high pressure discharge lamp is lighted and driven with relatively low drive power, the electrode temperature of the high pressure discharge lamp will be also relatively low and a flicker may occur.
A below-described technology has been suggested for avoiding such a flicker (see, for example, JP-A-2005-227748).
In the technology described in the document, when a discharge voltage of the high pressure discharge lamp varies, both of the magnitude and the frequency of the drive power supplied to the high pressure discharge lamp are increased. By increasing the magnitude and the frequency of the drive power of the high pressure discharge lamp, a temperature of gas in the high pressure discharge lamp is raised, thereby avoiding fluctuation in the discharge position in the high pressure discharge lamp (flicker).
The flicker is triggered not only by a reduction in the temperature of the electrodes but also by an unnecessarily formed projection other than the first projection on the electrode (hereinafter referred to as a second projection) can be exemplified.
For example, when the frequency of the drive current supplied to the high pressure discharge lamp is relatively high, temperature distribution on a surface of the electrodes becomes uniform. When the temperature distribution on the surface of the electrodes is uniform, the second projection other than the first projection is easily formed on the electrodes. Thus, when the second projection is formed on the electrodes, an arc origin is moved to the first or second projection, thereby causing a flicker.
In the technology described in the document, a flicker caused by the reduction in electrode temperature can be avoided by increasing the magnitude and the frequency of the drive power to the high pressure discharge lamp. However in the technology described in the document, since the magnitude and the frequency of the drive power supplied to the high pressure discharge lamp are increased, the second projection is easily formed on the electrodes, so that it is not possible to avoid a flicker caused by the second projection other than the first projection on the electrodes.
In addition, in the technology described in the document, since the magnitude and the frequency of the drive power supplied to the high pressure discharge lamp are increased, namely since the drive current of a relatively high frequency is supplied to the high pressure discharge lamp, the tip end of the electrodes wears, so that it is not possible to increase the longevity of the high pressure discharge lamp.
Therefore, there have been demands for a technology that can increase the longevity of the high pressure discharge lamp and avoid a flicker.